Meeting Abstract

101.6  Wednesday, Jan. 7  Sand Dolly: The adaptive significance of predator-induced cloning and size reduction in Dendraster excentricus plutei VAUGHN, D.; Univ. of Washington dvaughn@u.washington.edu

Predator-induced cloning (asexual reproduction), and reduced size as a consequence of cloning, suggests a novel adaptation to the threat of predation. Although cloning is a common reproductive strategy of many plants and animals, cloning in response to stimuli from predators has, at present, only been documented in the pluteus larvae of the Western sand dollar, Dendraster excentricus. Other studies report larval cloning in echinoderms under optimal conditions of food and temperature. A burst of asexuality should be favored when environmental conditions are conducive to growth, but it is less clear that cloning is advantageous when conditions indicate risk from predators. This study tests the hypothesis that the small size of predator-induced clones reduces vulnerability during direct encounters with planktivorous fish. As in an earlier study, cloning was induced by exposing the early stage plutei to stimuli from fish predators (i.e., external mucus). Cloning was inferred by an increase in larval density, a reduction in larval stage and size, and limited direct evidence of cloning by budding. All clones were smaller than uncloned sibling larvae, suggesting an advantage against visual predators. Pair-wise predation trials demonstrated that predatory fish ate more uncloned sibling plutei than clones. These results offer a new ecological context for asexual reproduction: rapid size reduction as a defense.